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<H2><A NAME="s4">4. Special keyboards - AT keyboards</A></H2>

<P><I>The AT keyboard adds a keyboard controller.
The numeric keypad is now separated from the main keyboard.
There is a single new key, with scancode 84 = <B>54</B>,
namely SysRq.</I>
<P>The protocol for AT and later keyboards differs from that for
XT keyboards. Some old keyboards have an XT/AT switch on the
backside that selects the appropriate protocol.
Other keyboard autodetect XT or AT mode.
<P>
<FIGURE>
<EPS FILE="absent">
<IMG SRC="xt-at-switch.jpg">
</FIGURE>
<P>
<P>The KeyTronic KB101-1 keyboard has four switches of which the first two
indicate the desired behaviour (00 - autodetect, 01 - unused,
10 - PC/XT, 11 - AT). Autodetect does not always work.
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